Editing Ten-digit dialing (section)

===Area code overlay===
By 1992, a new method of relief became available from the proliferation of [[electronic switching system]]s that were based on [[stored program control]] (SPC), which reduced the need for electromechanical extensions of the switching fabric. This made it possible to assign multiple area codes to a single numbering plan area. An [[area code overlay]] required additional technology in all affected switching systems to recognize the local area codes and select the appropriate routing for local calls, even within the wire center. This eliminated the possibility of maintaining seven-digit dialing, and required the dialing of ten digits for all calls.

Consumer groups and some state regulators, such as the Illinois Commerce Commission and Citizens Utility Board for northwest Chicago, and the NYS Public Service Commission in NYC, opposed the requirement with attempts at litigation.<ref>{{cite web|url=https://www.nytimes.com/2003/01/23/technology/the-10-or-11-digit-local-call-fosters-anxiety-and-shrugs.html|title=The 10- or 11-Digit Local Call Fosters Anxiety and Shrugs|date=2003-01-23|publisher=NY Times}}</ref><ref>{{cite web|url=https://www.chicagotribune.com/2001/07/25/days-are-numbered-for-7-digit-dialing/|title=Days are numbered for 7-digit dialing|work=Chicago Tribune}}</ref><ref>{{cite web|url=https://www.chicagotribune.com/2001/07/27/11-digit-dialing-due-for-everyone/|title=11-digit dialing due for everyone|work=Chicago Tribune}}</ref>
The added effort in remembering and dialing longer numbers was perceived as a disadvantage of [[overlay plan]]s, which were introduced to reduce the inconveniences associated with the traditional method of splitting an area. However, overlays have become the primary relief method and ten-digit dialing has become increasingly common in the U.S. and Canada.